Electrical apparatus



i C. G. SMITH ELECTRICAL APPARATUS Dec. 29, 1931 Original Filed July 501925 LOAD Patented Dec. 29, 1931 Bantu STAT S PAT Q F ciaasiisse, SMITH,or mnnronn, iviAssA oriusETrs,.-AssIGi\ oR, BY inEsnE AssieN arenas, T0RAYTHEON me, or CAMBRIDGE, 'miissaennsnrrs, a CORPORATION orMASSACHUSETTS ELECTRICAL APPARATUS Application filed July 30,1923, s mNo. 654,645. Renewed October 21, 1930.

The present invention relates to-electrical apparatus and moreparticularly to types'of electrical apparatus involving electricalconduction through a gaseous-medium;

It will be appreciated by those skilled in the art that one ofthe chiefdisadvantages of the usual forms of gaseous conduction-apparatus, Whichinvolve the ionization of anelectrically stressed gaseous inediuinfliesin the fact that continued. operation oflt he apparatus causes thedischarge tobecoiiie-irregular and erratic. This erratic operationarises'partly from the formation of a layer of ionized. gas adjacent theWalls of the containing receptacle, the action of this ionized gas beinto electrically charge the receptacleat various points, thus giving riseto non uniform and varying potential gradients throughout the gaseousregion. Furthermore, continued discharge in the region adjacenttheTWalls of the recptacle causes the Walls-to become blackened orcovered with a layer of conducting material, the formation of whichtends not only to aggravate the erratic operation of the device; butalso after long continued use, to often render the device practicallyinoperative.

The object of the present invention is to provide improvements ingaseous conduction devices of this general nature whereby regular anduniform operation of the apparatus may be secured.

In the usual constructions of gaseous discharge apparatus it has beenfound that the undesirable electrical charging of the receptacle arisesfrom the fact that electrostatic lines of force which may be enabled topass near the Walls of the receptacle ordinarily lie Within a gaseousregion of'considerable magnitude. lines of force in a largegaseous'regioncauses ionization of the gas, from Which follow thecharging of the receptacle and the consequent disadvantagesoutlinedabove. With the above object in View, however, I have discovered, thatby restricting the gaseous re gion through which such lines of force maypass, gaseous ionization in this region may be substantially eliminated.Accordingly, one feature of the present invention contem- The presenceof. electrostatic "ent invention, I 7

Although the features of the present in- 9 plates the provision of anelectrical appa ratus'h ving electrodes so maintained-in a gas filledreceptacle that the-gaseous regionsadjacent the Walls of the receptacleare of such restricted dimensions that ionizationis impossible. To thisend, the Width of such restricted gaseous regions should be comparableto the means free path of electrons in thegas, that is so short thatelectrons traveling directly across such regions produce insufficientionization to initiate substantial conduction. The mean free path ofelectrons, as herein connoted, is the average distance traveled byelectrons Without ionizing impact with gas molecules (or atoms); I It isbelieved that by the restriction of the gaseous region adjacent thewalls of the receptm'zle,- the operation of the present in ventiondepends largely upon theprinciples disclosed in theco-pending patent ofSmith, No. 1,545,207, granted July '7, 1925, Which describes a noveltype'of insu1atingappa ratus in which two electrodes are spaced so closetogether in a gas that gaseous ionization andconsequent conduction areimpossible. A gaseous region of such retricted magnitude'may be said topresent a practically infinite electrical resistance. therefore believedthat the same principle holds in'the present invention in which theelectrostati'c lines of force are constrained to pass through restrictedgaseous regions.

It is I,

;]Other features of the invention consist of certain novel features ofconstruction,

vantages "of which will be apparent to those skilledain the art fromthe. following 'description.

" The accompanying drawing illustrates the preferred form of a gaseousconduction tube embodying the several features of the pres vention areapplicable to substantially any 1 type of gaseous conduction apparatus,the illustrated embodiment of the invention employs the type ofapparatus described in the c'o-pending patent of Smith, No. 1,617,179,

granted Feb. 8, 1927. This application discloses a novel type ofrectifying device comprising two electrodes spacedapartin a gas, one ofthe electrodes being provided with a hollow space in which is permittedthe forma- I assemblies are conveniently supported upon a reentrant stemof the insulating receptacle and are preferably so constructed that theanode assembly is entirely surrounded by the cathode assembly, therebypreventing the discharge from affecting in any way the external partofthe receptacle. However, the stem upon which the electrode assembliesare mounted is maintained in the region of a fairly intense electricfield. According to the present invention, therefore, the electrodes areso mounted upon the stem that any electrostatic lines of force whichpassadjacent the stem are constrained to lie within a gaseous region of suchrestricted magnitude that ionization is prevented.

Referring particularly to the drawing, the preferred constructioncomprises a receptacle 2 consisting ofan external bulb 5 and a reentrantcylindrical stem 7, both being preferably of glass. The stem 7 isprovided with 'a'partition 8 of the form shown to divide the stem intotwo parts, the upperpart cominunicating with the rarefied gaseous mediumenclosed by the external bulb -5. The actual manufacture of theapparatus is carried out by mounting both electrode assemblies on thestem and thereafter sealing the stem to the external bulb portion afterwhich the tube is exhausted in the usual manner. The tube may then befilled with any gas at reduced pressure but it is preferred to'use aninert monatomic gas such as helium. The anode assembly comprises theanode proper 10 consisting preferably of a carbon button, a support 12for the button, an internal cylinder 1 1 and an external guard cylinder18. The two cylinders are connected by an annular supporting member 20having a flanged surface which is adapted to rest upon the upper part ofthe stem. To this end, it isdesirable-that the uppersurface of the stemshould be accurately ground. In order to hold the anode assembly rigid,the upper end of the guard cylinder 18 is spun over the edge of'thecarbon button 10, as indicated in the drawing. The supporting member 20has a depending cylindrical portion 21 which is adapted to fit snuglyagainst the internal surface of the stem and an upstanding cylindricalportion 22 which is attached to the cathode assembly includes thecathode proper which is constructed with a base portion 30 having anupstanding sleeve 32 communicating with a hollow space. enclosed by thehollow cylindrical portion 3a. The base 30 and the portion 84 arepreferably constructed of carbonf The base 30 rests upon a flange 36 of'a cathode guard cylinder 38 which is of such dimensions that itsinternal surface is spaced from the surface of the anode guard cylinder18 by a distance which is so short that ionization between the two guardcylinders is impossible. The two parts of the cathode are connectedtogether and supported upon the flange 86 by a flange member 10 to whicha suitable wire a1 is soldered at diametrically opposite points, thewire being adapted to pass over the hollow portion 3d of the cathode.The guard cylinder 38 is supportedupon a guard ring 42 which is incontact at its lower end with the stem 7 and which is provided with arecess l at its upper end, this recess being comparable in width to thedistance separating the stem 7 and the guard cylinder 18. Also the upperend of the guard ring 42 is spaced fromthe lower end of the guardcylinder 18 by an equally short distance. I According to the inventiondisclosed in the co-pending Patent No. 1,617,- 179, the parts are sodisposed that the surfaces of the anode 10 and the cathode base 30 arealso separated by a distance which is comparable to the mean free pathof electrons in the gas. The cathode assembly'is rigidly maintained onthe stem by means of a cylindrical member 16 which is provided with alead wire 16 to the other.

The simple rectifying circuit shown in connection with the apparatusincludes an alter- .nating current generator 52, a transformer 54:, thetube 2, and a suitable load, all connected as indicated.

It will be seen that inasmuch as the anode assembly is entirelysurrounded by the cathring 42 and may thus ode assembly, the tube cannotbe injuriously affected in any way by the discharge. The close spacingbetween'the guard cylinders 18 and 38 renders discharge impossibleexcept between the active surfaces of the electrodes themselves.Furthermore, the glass stem 7 is not placed under an excessiveelectrical stress since the path afforded for electrical conductionthrough the glass extends from the supporting member 20 to the lowerpart of the guard be made sufliciently long to prevent any injurious efiects within the glass itself. 7 According to the present invention, thelower portion of the guard cylinder l8 and the upper part of the guardring 42 are each separated from the material of the stem 7 by such ashort distance that any electrostatic lines of force which may passwithin the included region are powerless to initiate ionization.

Although the illustrated embodiment of the invention is designed toprevent undesirable discharge adjacent the surface of the reentrantstem, it is understood that the stem is to be consioered as part of thecontaining receptacle and that the walls of the receptacle, as that termis used herein and in the mended claims are to be considered asincluding the surfaces of the stem or any other parts of the receptacleadjacent which any electrostatic lines of force may pass.

This application is in part a continuation of my Patent #1,617,179,granted February a, 1927.

The invention having been described, what is claimed is:

1. A gaseous discharge rectifier comprising a sealed container having areentrant stem, said stem having a cylindrical portion extendinginwardly into said container, a cathode and anode mounted on said stemin spaced relation to each other, one of said electrodes being supportedby concentric meta-l cylinders, the distance between which issubstantially equal to the thickness of the cylindrical portionextending from said stem, said concentric members beingmountedrespectively on the inside and outside of said projectingportion, an annular member anchored between said concentric members andserving as a stop for the edge of said projecting portion and a springconnected to said electrode and serving as a lead therefor, pulling saidelectrode down to maintain said concentric members firmly against saidprojecting portion.

2. A gaseous discharge rectifier comprising a sealed container having areentrant stem, said stem being provided with a cylindrical portionprojecting inwardly, a cathode and an anode spaced apart therein andmounted on said stem, both electrodes being supported by concentriccylindrical metallic members, said anode being supported by two theexternal bulb portion ofsuch members engaging the inside and outsidewalls respectively of said projecting portion of said stem, an annularmember between said anode supporting concentric members, joining saidmembers and serving as a stop for the edge of said projecting stemportion, and a spring connected to the anode and serving as a leadtherefor, pulling said anode, and said anode supporting concentricmembers downwardly into firm engagement with said projecting stemportion.

3. A gaseous discharge device comprising a sealed container having areentrant stem, said stem having a hollow portion extending inwardlyinto said container, two electrodes mounted on said stem in spacedrelation to each other, one of said electrodes being supported bymetallic members, said members being mounted respectively on the insideand outside of said hollow portion, a member fastened between saidmetallic members and serving as a stop for the edge of said hollowportion, and means for maintaining said last named electrode and itssupporting members on said hollow portion.

4. A gaseous discharge device comprising a sealed container having areentrant stem, said stem having a hollow portion extending inwardlyinto said container, two electrodes mounted on said stem in spacedrelation to each other, one of said electrodes being supported bymetallic members, said members being mounted respectively on the insideand outside of said hollow portion.

A gaseous discharge device comprising a sealed container having areentrant stem, said stem having a hollow portion extending inwardlyinto said container, a cathode and an anode supported on said stem, saidanode being supported by a supporting member on said hollow portion, aprojection on said sup porting member engaging a shoulder on said hollowportion, and means for holding said anode and supporting member withsaidprojection against said shoulder.

gaseous conduction device comprising a hollow cathode with an openingtherein, an anode having a surface presented to the interior of thecathode through said opening, a sealed container having a reentrantstem, said stem having a hollow portion extending inwardly into saidcontainer, a supporting member for said anode engaging the outside andinside. of said hollow portion, said cathode being supported from saidstem in spaced relationship to said anode.

CHARLES G. SMITH.

